Theories on phage lambda's lysogenic decision suggest that by allocating a subpopulation of infections to the dormant lysogenic state, survival of the population is ensured through uncertain deleterious environments. For lambda, lysogenization increases with the number of infecting phages, a quantity called the multiplicity of infection or MOI. However, theory predicts enhanced survival if lysogenization was independent of, or decreased with, MOI so long as some percentage of infections result in lysogeny. Using agent-based modeling, we compete phage strains with different MOI-dependencies against each other in variable environments. We discover that certain MOI-dependencies can be naturally selected over others, suggesting that evolution quantitatively tuned lambda's MOI-dependence to maximize survival.

*This research was supported by National Institutes of Health National Institute of General Medical Sciences (NIH-NIGMS) grant R01GM107597 and administrative supplement 3R01GM107597-02S1 to L.Z. and G.B., as well as by NIH-NIGMS grant R35GM122561 and by a Laufer Center for Physical and Quantitative Biolog